Date: Fri, 20 Oct 2006 08:41:16 +0100 (BST) From: Robert Watson <rwatson@FreeBSD.org> To: Paul Allen <nospam@ugcs.caltech.edu> Cc: freebsd-security@freebsd.org, freebsd-stable@freebsd.org Subject: Re: FreeBSD 4.x EoL Message-ID: <20061020083937.E32598@fledge.watson.org> In-Reply-To: <20061020011549.GD30707@riyal.ugcs.caltech.edu> References: <453531C9.7080304@freebsd.org> <45355C6E.5030703@jim-liesl.org> <20061020004915.V32598@fledge.watson.org> <20061020011549.GD30707@riyal.ugcs.caltech.edu>
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On Thu, 19 Oct 2006, Paul Allen wrote: >> While possibly not advisable in the long term, I ran a 4.x postfix and >> cyrus server install on 6.x using compat4 for about six months without >> problems. The place where it gets tricky is updating the 4.x binaries, >> which requires a 4.x chroot, since I was running a native 6.x userland for >> everything else. I've now gotten over that, but it worked quite well and >> was extremely useful that I could avoid doing the upgrade all at once -- >> upgrade the OS first, let it settle, then upgrade the applications. The >> only issue I ran into was actually that the location of the Cyrus sasl unix >> domain socket had moved, and once I tracked that down, all was well (so not >> a FreeBSD nit, an application nit). > > Let me toss a bit of caution from experience regarding this: > > I too ran such 6.x system. It had a jailed FreeBSD 4.x userland (restored > and modified from the original FreeBSD 4.x backups). Almost everything > worked properly--but there were some strange vm related inconsistencies > (exposed by a program rolling its own gc implementation and using mprotect > and SEGV). > > Obviously this was an unusual case but it's unfortuantely proof that some > things escape having the necessary compat lines in your kernel conf. > > Still I counted myself lucky. When you recompiled the application for 6.x, did the problem go away? I guess I wouldn't entirely preclude an application bug, a 4.x library bug, or a 6.x compat/non-compat bug being responsible. Since 6.x is a fairly major upgrade, there are significant changes in VM (which might well affect, for example, memory layout), etc, so it could well be that it triggered a bug in the GC. Robert N M Watson Computer Laboratory University of Cambridge
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